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<p>Chemical dynamics simulations were carried out to investigate the association and dissociation of the benzene–hexachlorobenzene (Bz–HCB) complex at 1000–2000 K with impact parameters up to 10 Å. Two classes of complexes, short- and long-lived, were identified based on distance and lifetime criteria. Association probability decreased from ~40% at 1000 K to ~10% at 2000 K, with lifetimes of 1.7–26.6 ps. Arrhenius analysis of association rate constants showed reduced stability of the complexes at higher temperatures. Dissociation rates increased with temperature at finite impact parameters, while remaining nearly invariant at <i>b</i> = 0.0 Å. Comparison with benzene dimers and Bz–hexafluorobenzene (Bz–HFB) showed stronger stability of Bz–HCB due to π–π interactions. Rice–Ramsperger–Kassel (RRK)-based analysis indicated incomplete vibrational energy randomization in all the complexes. However, Bz–HCB exhibited the highest effective degrees of freedom, consistent with enhanced mode–mode coupling leading to back-and-forth energy transfer among its vibrational modes that slows its dissociation relative to Bz–HFB and Bz<sub>2</sub>.</p> Graphical abstract <p>The graphical abstract compares benzene dimer (Bz<sub>2</sub>), benzene–hexafl uorobenzene (Bz–HFB), and benzene–hexachlorobenzene (Bz–HCB) complexes. Complex stability increases from Bz<sub>2</sub> to Bz–HCB. Association probability decreases with increasing temperature, whereas the ensuing dissociation rate increases. Additionally, the association rate increases from Bz<sub>2</sub> to Bz–HCB, while the ensuing dissociation rate follows the opposite trend, indicating enhanced intermolecular stability in halogenated complexes.</p>

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Chemical dynamics simulations on the association and ensuing dissociation of the benzene–hexachlorobenzene complex and comparison with benzene dimer and benzene–hexafluorobenzene complexes

  • 期刊论文

  • 发表日期：

    2026年7月3日

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  • Basudha Deb,
  • Nabam Yal,
  • Himashree Mahanta,
  • Amit Kumar Paul

摘要

Chemical dynamics simulations were carried out to investigate the association and dissociation of the benzene–hexachlorobenzene (Bz–HCB) complex at 1000–2000 K with impact parameters up to 10 Å. Two classes of complexes, short- and long-lived, were identified based on distance and lifetime criteria. Association probability decreased from ~40% at 1000 K to ~10% at 2000 K, with lifetimes of 1.7–26.6 ps. Arrhenius analysis of association rate constants showed reduced stability of the complexes at higher temperatures. Dissociation rates increased with temperature at finite impact parameters, while remaining nearly invariant at b = 0.0 Å. Comparison with benzene dimers and Bz–hexafluorobenzene (Bz–HFB) showed stronger stability of Bz–HCB due to π–π interactions. Rice–Ramsperger–Kassel (RRK)-based analysis indicated incomplete vibrational energy randomization in all the complexes. However, Bz–HCB exhibited the highest effective degrees of freedom, consistent with enhanced mode–mode coupling leading to back-and-forth energy transfer among its vibrational modes that slows its dissociation relative to Bz–HFB and Bz2.

Graphical abstract

The graphical abstract compares benzene dimer (Bz2), benzene–hexafl uorobenzene (Bz–HFB), and benzene–hexachlorobenzene (Bz–HCB) complexes. Complex stability increases from Bz2 to Bz–HCB. Association probability decreases with increasing temperature, whereas the ensuing dissociation rate increases. Additionally, the association rate increases from Bz2 to Bz–HCB, while the ensuing dissociation rate follows the opposite trend, indicating enhanced intermolecular stability in halogenated complexes.